Self leveling dispenser

ABSTRACT

A self-leveling dispenser provides a rack supporting a stack of trays within a frame. A reversible motor drivably connected to spiral shafts mounted at the corners of the frame rotates the shafts to provide upward or downward movement of the rack, which is supported on the spiral shafts by threaded sleeves. An upper sensor mounted to the frame is operably connected to the motor to move the rack downward upon detecting a tray at an upper horizontal level above a desired height. A lower sensor mounted to the frame is operably connected to the motor to raise the rack upon sensing the absence of a tray at a lower horizontal level below the desired height. The sensors cooperate to automatically and continuously reposition an uppermost portion of a top tray in the stack at the desired height with respect to the frame, thereby to facilitate dispensing of dishes or food products.

This is a continuation, of application Ser. No. 07/264,089, filed Oct.28, 1988 now abandoned.

FIELD OF THE INVENTION

This invention relates to dispensers and, more particularly, toautomatic self-leveling dispensers.

BACKGROUND OF THE INVENTION

Over the course of a typical day, cafeterias generally use, wash andre-use a large number of dishes, e.g., plates, cups, and glasses on acontinuous basis. A series of manually portable dishware trays, eachproviding a number of top opening compartments sized to receive one ormore pieces of dishware, is often used by the cafeteria to facilitatedispensing of the dishes to retail customers. The trays are usuallysized and structured to be stacked vertically one on top the other inthe cafeteria line.

Dishware dispensers are well known to the prior art. A dishwaredispenser supports a number of stacked dishware trays upon a rack withina box-like, mobile frame. When the supply of dishes, e.g., glasses, inthe top tray is exhausted, the top tray is removed to provide access toglasses in the tray immediately below. Subsequent exhaustion of glassesin the tray just below requires removal of that tray, and so on.Eventually, this results in an empty dishware dispenser, whereuponanother stack of trays containing clean dishes is placed upon the rack.

Self leveling dishware dispensers are known which provide a rack that isvertically movable with respect to the frame. The rack, in commercialembodiments of which we are aware, is spring biased upwardly to maintainthe top dish tray in the stack at a relatively constant heightregardless of the number of trays in the stack. As the weight of thestack decreases, i.e., as dishes and trays are removed, a springmechanism forces the rack upward until a new equilibrium is reachedbetween tray weight and spring force. Theoretically, this should placethe top tray at the desired height for use by the customer.

A significant inherent problem exists in maintaining the properdispensing height of a self leveling dishware dispenser of the springelevated type. This problem occurs as a result of improperly filledtrays, partially filled trays and changing weights and sizes of dishwareitems to be dispensed. So designers, contractors and suppliers mustcontinuously verify the sizes and weights of the items to be dispensedin order to properly size the dishware dispenser's spring mechanism. Inother words, the performance of such prior art dishware dispensersdepends upon proper initial spring calibration, and reliable adjustmentmechanisms, which allow spring adjustment after the dispenser has beenin use for a period of time. Otherwise, the dispenser will not beproperly responsive to the trays from which dishware is to be dispensed.

Accordingly, it is the objective of this invention to provide animproved self-leveling dispenser which overcomes the disadvantagesassociated with dishware dispensers of the spring mechanism type.

SUMMARY OF THE INVENTION

A self-leveling dispenser, according to a preferred embodiment of theinvention, includes a rack for holding stacked trays, vertical spiraldrive shafts, a reversible motor, a chain and sprocket assembly, andtray position sensors. The spiral drive shafts are located at the rack'scorners and rotate relative thereto. The rack is supported upon theshafts by followers fixed to the rack. The chain and sprocket assemblydrivably connects the motor to all the drive shafts to raise or lowerthe rack as the shafts are rotated by the motor.

Upper and lower tray sensors are connected with the motor and operate tomaintain the top tray at the desired dispensing height. Upper and lowertravel limit switches are located at the upper and lower ends of theshafts, respectively, to prevent over travel of the rack into the frame.An override circuit which connects the sensors to the motor preventsboth an "up" and a "down" signal from being simultaneously transmittedto the motor.

In use, and upon detecting the presence of a tray newly placed on top atray stack where the previous top tray is at the desired dispensingheight, the upper tray sensor signals the motor to rotate the shafts soas to lower the rack a distance about equal to the height of that tray,thereby lowering all the trays on the rack until the newly placed traybecomes the top tray at the desired dispensing height. Upon detectingthe absence of a tray at the desired dispensing height such as wouldoccur when an empty tray has been removed, the lower sensor signals themotor to rotate the shafts so as to raise the rack a distance aboutequal to the height of the new top tray that remains on the rack,thereby raising all the trays on the rack until the new top tray is atthe desired dispensing height. So the upper and lower sensors cooperateto automatically and continuously reposition a new top tray on the stackof trays at the desired dispensing height regardless of the number oftrays in the stack, and regardless of whether the new top tray is a fulltray manually added to the top of the tray stack in the dispenser or isa full tray already in the tray stack which is exposed when an emptytray is manually removed from the top of the tray stack.

More specifically, with no trays stacked upon the rack, the rack islocated at an uppermost position relative to the spiral shafts. Undernormal conditions, this uppermost position is below the upper sensorbecause the upper sensor would signal the motor to lower the rack untilnothing is sensed by the upper sensor. If the upper sensor fails, therack's uppermost position will be the level at which the upper limitswitch stops upward movement of the rack. If desired, the upper limitswitch may be positioned to detect and stop the rack prior to its beingraised to the upper horizontal level. Placement of a stack of trays uponthe rack causes the upper sensor to detect the presence of a side of atray at the upper sensor level and to signal the motor to rotate theshafts to move the rack downward. The rack will move downward so long asany tray is detected by the upper sensor, i.e., until the top tray onthe stack has moved below the upper sensor. If too many trays arestacked onto the rack at one time, i.e., if the stack is too tall forthe travel path length of the rack, downward movement of the rack willcontinue only until the rack contacts the lower travel limit switch todisengage the motor. No further movement of the rack will occur untilenough trays have been removed from the stack to activate the lowersensor. With the lower sensor activated, the motor operates to raise therack until a tray is detected by the lower sensor. When the top tray atthe desired height has been emptied and removed, the next tray will beautomatically raised to the desired height, and so on until furtherupward travel of the rack is inhibited by either the upper limit switchor the upper sensor.

The automatic self-leveling dispenser of this invention providesdishware or food product dispensing at a relatively constant desiredheight regardless of variation in the weight or types of items beingdispensed. Moreover, while a spring activated dishware dispenserrequires occasional recalibration of its springs, this automaticdispenser does not require any type of recalibration to dispensedishware or food products at the desired height.

These and other advantages of the invention will be more readilyunderstood in light of the following detailed descriptions and thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a partially cut away perspective view of an automaticself-leveling dish dispenser according to a preferred embodiment of theinvention;

FIG. 2 is a bottom plan view of the automatic dishware dispenser shownin FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1;

FIG. 4 is a diagram showing the electronic circuitry connected betweenthe upper and lower sensors and the motor for the dishware dispensershown in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1-4 show an automatic self-leveling dispenser 10 according to apreferred embodiment of the invention. As shown in FIG. 1, a box-likeframe 12 provides exterior structural support for the dispenser 10.Preferably, frame 12 is mounted on casters 13. Outer walls 14 and topwall 15 enclose the frame 12, and the top primarily remains open tomanual access for receipt of trays 33. The frame 12, walls 14 and top 15are preferably metal, though any structurally rigid material willsuffice.

Adjacent a top portion 16 of the frame 12, horizontally disposed plates17 extend inwardly to mount spiral drive shafts 18 to the frame 12 bytop roller bearing bushings 19. At the bottom 20 of the frame 12, thespiral shafts 18 are supported on base platforms 22 by bottom rollerbearing bushings 23. The roller bearing bushings 19 and 23 render theshafts 18 rotatable with respect to the frame 12. A rack 25 is supportedupon the shafts 18 by four threaded followers or sleeves 26 fixed to therack, and the rack 25 can be moved upwardly or downwardly by rotatingthe shafts 18. Rack 25 supports a desired number of trays 33 in stackedarrangement. The trays 33 are typically plastic, and are open at the topto permit access to dishware, e.g., glasses 34, or to food products,e.g., individual serving milk cartons (not shown), located therein. Inthis application, the term "dishware" is meant to refer to cups, bowls,glasses, mugs, plates, etc. Also in this application, the term "tray" ismeant to refer to a reusable carrier within which dishware or foodproduct can be placed, as well as a non-reusable carrier such as a boxor carton within which food products, e.g., ice cream bars or popsicles,are packaged and/or shipped.

As shown in FIG. 2, a motor 28 is drivably connected to the spiral driveshafts 18 by a chain and tension sprocket assembly 30. The chain 29 ofthis assembly is oriented in a horizontal plane positioned beneath thehorizontal rack 25, and connects with each shaft 18 by a driven sprocket49. Thus, rotational movement of the motor 28 is imparted to all theshafts 18 by chain 29 to raise or lower rack 25. A motor sprocket 46mounted on motor shaft 47 rotates with the motor shaft 47 to imparteither clockwise or counterclockwise (as viewed in FIG. 2) motion tochain 29. Two tension sprockets 48 direct chain 29 to the four cornersprockets 49.

An electrical conduit 36 carries electrical connections from the motor28 to a housing 38 mounted adjacent top portion 16 of the frame 12. Thehousing 38 houses sensing means in the form of an upper infrared sensor39 and a lower infrared sensor 40 in spaced vertical relation, samebeing located at the desired dispensing height for the glasses 34. Asshown in FIG. 3, upper sensor 39 is located at an upper level 41, andlower sensor 40 is located at a lower level 42. The gap between upperand lower levels 41 an 42 defines the desired dispensing height 43 atwhich a top tray 45 in the stack will reside.

Upon detecting the presence of a tray at upper level 41, upper sensor 39signals the motor 28 to lower rack 25. Motor 28 continues to lower rack25 until the top edge 44 of the top tray 45 moves below upper level 41,i.e., until the top tray 45 moves below upper sensor 39, whereupon powerto motor 28 is disconnected and lowering movement of the rack isstopped. When the supply of glasses 34 or food product residing in thetop tray has been exhausted, an operator removes the top tray, thusvacating the lower level 42. Upon detecting the absence of a tray at thelower level 42, lower sensor 40 signals the motor 28 to raise the rack25 until to edge 44 of the next tray in the stack has moved into level42, whereupon power to motor 28 is disconnected and raising movement ofthe rack is stopped.

An upper limit switch 52 prevents upward over travel of rack 25 into theframe 12, as explained previously. Switch 52 is actuated upon contactwith the rack 25 and is preferably mounted to an underside of topportion 16, just above upper level 42, as shown in FIG. 3. If the lowersensor 40 continues to transmit a raise signal despite the presence ofthe rack 25 at the lower level 42, and the rack 25 raises beyond level42 into contact with switch 52, the motor 28 will be disconnected.Similarly, a lower limit switch 54, also actuated by contact, is mountedto one of the plates 22 to prevent downward over travel of rack 25 intothe frame 12. Limit switch 52 is connected to electrical circuitry inhousing 38 via conductors 85a and 85b. Similarly, limit switch 54 isconnected to electrical circuitry in housing 38 via conductors 86a and86b.

Although a particular frame height will dictate a preferable number oftrays for stacking within the frame 12, additional trays may be stackedabove upper level 41 if desired. Such overstacking will eventuallyactivate switch 54 and stop the motor 28 because the rack 25 will not beable to move downward far enough to place the top tray below level 41.The upper stacked trays 33 will remain in place, and no up signal willbe provided until all of the stacked trays located above the lower level42 have been removed.

A circuit schematic showing the electrical circuit components connectedbetween the upper sensor 39 and the lower sensor 40 and motor 28 toprovide the desired lowering and raising of rack 25 is shown in FIG. 4.Each of the sensors 39, 40 is preferably a photoelectric sensor havingboth a transmitter and a receiver to cooperatively sense transparent oropaque objects within a predetermined horizontally directed range 50,preferably about 4". A component manufactured and sold by Omron asCatalogue No. E3F has proved to be a suitable photoelectric sensor forthe purposes of this invention. The sensors 39 and 40 have firstterminals 55 and 56, respectively, connected to a +12 volt power source,and third terminals 58 and 59, respectively, connected to -12 volts. Amiddle terminal 61 of sensor 39 is simultaneously input to a NAND gate66 and a 555 timer 67. The timer 67 incorporates a time delay factorinto the circuit to prevent instantaneous raising or lowering of therack 25 upon sensing the inadvertent and/or temporary placement of ahand or other object within the detection range 50.

The timer 67 inverts the signal and inputs it to an inverter 68 whichinverts it again before input into NAND gate 66. Upon detecting anobject at the upper horizontal level 41, both inputs to NAND gate 66will be high resulting in a low output at node 70. This low output isinverted by inverter 71 and input to transistor 72, causing it toconduct and to close normally open relay 73. Closing of relay 73 causesthe motor 28 to rotate the shafts 18 for downward movement of the rack25. Movement will continue so long as a tray presence is sensed bysensor 39, or until lower limit switch 54 detects the rack 25 and opensthe circuit.

During downward movement of rack 25, a low signal at NAND gate 66produces a high signal out of inverter 75 to insure a low output for NORgate 76, thus preventing transistor 77 from conducting. Conductionthrough transistor 77 controls the position of normally open relay 78,which connects power to the motor 28 to raise the rack 25. Thus, thiscircuit provides an override safety feature which prevents thesimultaneous signalling to the motor 28 to both raise and lower the rack25. So long as upper sensor 39 senses an object at upper level 41,regardless of what is sensed by lower sensor 40, transistor 72 willconduct and transistor 77 will not conduct, thus lowering the rack 25.

When the top edge of a top tray has moved below the upper level 41, theoutput to NAND gate 66 will go high resulting in a low output frominverter 75. With the low output from inverter 75 fed into NOR gate 76,conduction through transistor 77 will be controlled by the other inputto NOR gate 76, the input connected to middle terminal 62 of the lowersensor 40. The absence of an object at lower horizontal level 42 willcause a low signal from second terminal 62 of lower sensor 40 to beinput into NOR gate 76, causing the output to go high. Transistor 77will conduct and close normally open relay 78 to cause the motor 28 torotate the shafts 18 in order to raise the rack 25. Raising willcontinue until the uppermost portion of a top tray is sensed by lowersensor 40 to switch off the output of NOR gate 76, and thus turn offtransistor 77.

The position of the rack 25 can also be raised or lowered manually byswitches 81 or 82, respectively, which may be mounted to the side ofhousing 38 at a location not shown. According to the circuit depicted inFIG. 4, in the manual mode, switches 81 and 82 operate independently ofeach other, and should never be switched on simultaneously. On the otherhand, in the automatic mode both switches should be on at the same time.The manual switches 81 and 82 are connected on one side to motor 28 viaconductors 87 and 88, respectively. On the other side, in the manualmode, switches 81 and 82 are connected to an electrical conductor 89,which conveys power from a power connection point 94 at the motor 28 tohousing 38. In the automatic mode, switches 81 and 82 are connected toconductors 86b and 86b, respectively. An electrical conductor 91 conveyspower from the power connection point 94 at the motor to housing 38 forthe automatic mode. Between the motor 28 and the housing 28, conductors87, 88, 89 and 91 reside within conduit 36. The a.c. connections to themotor 28 are preferably routed from power connection points 93 and 94via a power cord (not shown) to a standard 120 volt, 60Hz power outlet.

The motor 28 is preferably an a.c. snychronous motor operated at a speedof 72 revolutions per minute, and capable of raising the rack 25 at arate of about 12 inches per minute. A motor 28 capable of providing 750ounce inches of torque has proved sufficient for this invention. D.C.power for the circuitry in housing 38 can be supplied either bybatteries mounted therein or by rectified a.c. routed to the housing 38through another conductor in conduit 36.

While I have described a preferred embodiment of an automaticself-leveling dish dispenser according to the invention, it is to beunderstood that the invention is not limited thereby and that, in lightof the present disclosure of the invention, various other alternativeembodiments will be apparent to a person skilled in the art.Accordingly, it is to be understood that changes may be made withoutdeparting from the scope of the invention as particularly set forth andclaimed

I claim:
 1. A self leveling dispenser comprisinga rack supported forvertical movement relative to ground, said rack being adapted to supporta desired number of trays in stacked arrangement one on top the other,at least one drive shaft connected to said rack for rotation withrespect thereto, a reversible motor drivably connected to said driveshaft, and a sensor device located above said rack and operativelyconnected to said motor, said sensor functioning to sense the presenceand absence of trays at the vertical location of said sensor toautomatically and continuously raise and lower said rack upon removal oraddition of a tray or trays so that a top tray on said rack will belocated at a desired dispensing height relative to ground.
 2. Adispenser according to claim 1, said sensor device comprisingan uppersensor located at an upper level, said upper sensor being adapted toprovide a down signal to said motor to vertically lower said rack uponthe detection of a tray at said upper level, and a lower sensor locatedat a lower level, said lower sensor being adapted to provide an upsignal to said motor to vertically raise said rack upon detecting theabsence of a tray at said lower level, said desired dispensing heightbeing defined by the vertical position of said upper and lower sensors.3. A dispenser according to claim 1 comprisingan upper limit switchlocated at an upper level, said upper switch being operatively connectedto said motor to disable upward movement of said rack upon said upperswitch detecting the presence of said rack adjacent the top end of itstravel path, and a lower limit switch located at a lower level, saidlower switch being operatively connected to said motor to disabledownward movement of said rack upon said lower switch detecting thepresence of said rack adjacent the lower end of its travel path.
 4. Adispenser according to claim 3 comprisinga frame, and at least two driveshafts connected to said rack, said drive shafts being verticallyoriented, and said drive shafts being located at spaced positions aboutthe periphery of said rack.
 5. A dispenser according to claim 4, saiddrive shafts being spiral drive shafts mounted to said frame, andatleast two followers fixed to said rack, said followers receiving saidspiral shafts in driving relation therewith.
 6. A dispenser according toclaim 4 comprisinga chain operatively connecting said drive shafts withsaid motor to impart rotational movement to said shafts upon operationof said motor, said chain being oriented in a generally horizontal planebeneath said rack.
 7. A dispenser according to claim 2 comprisingasafety circuit operatively connected to said upper and lower sensors toprevent the simultaneous providing of both a raise signal and a lowersignal to said motor.
 8. A self leveling dispenser comprisinga frame, atleast two spiral drive shafts mounted to said frame for rotation withrespect thereto, a reversible motor mounted to said frame and drivablyconnected to said spiral shafts by a chain and sprocket assembly, a racksupported within said frame on threaded sleeves meshed with said spiralshafts, said rack being vertically movable with respect to said frameupon rotation of said shafts by said motor, said rack being adapted tosupport trays in stacked arrangement, an upper sensor mounted to saidframe at an upper level and adapted to provide a down signal to saidmotor to vertically lower said rack upon the detection of a tray at saidupper level, a lower sensor mounted to said frame at a lower level andadapted to provide an up signal to said motor to vertically raise saidrack upon detecting the absence of a tray at said lower horizontallevel, said desired dispensing height being defined by the verticalposition of said upper and lower sensors, said sensors cooperating toautomatically and continuously reposition a top tray of a stack of trayssupported on said rack at the desired dispensing height, an upper limitswitch mounted to said frame and operatively connected to said motor todisable upward movement of said rack upon detecting the presence of saidrack adjacent the top end of its travel path, and a lower limit switchmounted to said frame and operatively connected to said motor to disabledownward movement of said rack upon detecting the presence of said rackadjacent the lower end of its travel path.
 9. A self leveling dispensercomprisinga rack supported for vertical movement relative to ground,said rack being adapted to support a desired number of trays in stackedarrangement one on top the other, a reversible motor drivably connectedto said rack, and a sensor device located above said rack andoperatively connected to said motor, said sensor functioning to sensethe presence and absence of trays at the vertical location of saidsensor to automatically and continuously raise and lower said rack uponremoval or addition of a tray or trays so that a top tray on said rackwill be located at a desired dispensing height relative to ground.
 10. Adispenser according to claim 9, said sensor device comprisingan uppersensor located at an upper level, said upper sensor being adapted toprovide a down signal to said motor to vertical lower said rack upon thedetection of a tray at said upper level, and a lower sensor located at alower level, said lower sensor being adapted to provide an up signal tosaid motor to vertically raise said rack upon detecting the absence of atray at said lower level, said desired dispensing height being definedby the vertical position of said upper and lower sensors.
 11. Adispenser according to claim 9 comprisingan upper limit switch locatedat an upper level, said upper switch being operatively connected to saidmotor to disable upward movement of said rack upon said upper switchdetecting the presence of said rack adjacent the top end of its travelpath, and a lower limit switch located at a lower level, said lowerswitch being operatively connected to said motor to disable downwardmovement of said rack upon said lower switch detecting the presence ofsaid rack adjacent the lower end of its travel path.
 12. A dispenseraccording to claim 11 comprisinga frame, at least one drive shaftconnected to said rack, and at least one follower fixed to said rack,said follower receiving said shaft in driving relation therewith.
 13. Adispenser according to claim 12 comprisingat least two drive shafts andat least two followers, said drive shafts being generally verticallyoriented, and a chain operatively connecting said drive shafts with saidmotor to impart rotational movement to said shafts upon operation ofsaid motor, said chain being oriented in a generally horizontal planebeneath said rack.
 14. A dispenser according to claim 10 comprisingasafety circuit operatively connected to said upper and lower sensors toprevent the simultaneous providing of both a raise signal and a lowersignal to said motor.